20 CFR 404.780: Evidence of “good cause” for exceeding time limits on accepting proof of support or application for a lump-sum death payment.

(a) When evidence of good cause is needed. We may ask for evidence that you had good cause (as defined in § 404.370(f)) for not giving us sooner proof of the support you received from the insured as his or her parent. We may also ask for evidence that you had good cause (as defined in § 404.621(b)) for not applying sooner for the lump-sum death payment. You may be asked for evidence of good cause for these delays if—

(1) You are the insured person's parent giving us proof of support more than 2 years after he or she died, or became disabled; or

(2) You are applying for the lump-sum death payment more than 2 years after the insured died.

(b) What evidence of good cause is needed. We will ask for the following evidence of good cause:

(1) Your signed statement explaining why you did not give us the proof of support or the application for lump-sum death payment within the specified 2 year period.

(2) If the statement in paragraph (b)(1) of the section or other evidence raises a reasonable doubt whether there was good cause, other convincing evidence of this.